Field Guide · Instrumentation
Why your numbers never agree, and how to spec a setup that measures the truth — GA4 events, Meta Pixel + Conversions API, attribution, and the privacy layer, for the marketer or PM who has to diagnose the discrepancy, not write the tag.
⚠️ PERISHABLE — platform mechanics shift fast. Verified Jul 2026; re-check current GA4 / Meta docs. Review by Jan 2027.